Ultraviolet tube



- 7, 1943- c. w. MCKINLEY 1x21- AL 2,336,183

I ULTRAVIOLET TUBE Filed May 1o, 1941 Patented Der.. 7, las@ i UNITED essaies otraavrom'r "rima tion ol? Delaware Application May l0, lillfserial No. 392,@28

(Cl. tid-209) 7 Claims.

This invention relates to means for producing ultraviolet rays and more specifically to ultraviolet apparatus which may be operated from a low voltage initial source. y

Under certain circumstances it might be necessary to provide means for seeing' certain objects or configurations at night which are not illuminated themselves and upon which no light Waves of ordinary length are allowed to impinge. In other words, when it is necessary to resort to the so-called blackout methods as employed in England during raids, some means for identifying various objects or highways are necessary in order to allow movement of either civilians or troops.

It is therefore an object of our present invention to provide a means for identifying or locating certain objects along the sides of a highway so that traiic may flow without the danger of the identiflcation of such marks from the air. The type of system broadly considered here is that of utilizing luminous paint to cover certain posts or other identifying marks at certain intervals along the side of highways which of course would be of sufficiently low intensity that they would not be visible to the eye unless some ultraviolet rays were allowed to impinge thereon and cause the radioactive material to glow with sufficient luminosity to be visible. These could be spaced at regular intervals along the sides of the highway and so painted and then vehicles which it was desired to drive thereon could have some ultraviolet light means projectible forward in the same manner as the ordinary headlight beam does at present. These ultraviolet beams would then cause these markers to glow sufliciently to be visible to the driver in a horizontal distance, but would not be visible at any vertical distance, and thus the vehicle could' be operated along the outlined highway` to provide a source of ultraviolet ray which may be carried upon 'a mobile vehicle.

It is a still further object of our invention to provide an inexpensive, rugged source of ultra-` violet ray for application to the vehicle head-v light assembly which will operate on the normal storage battery voltage of the vehicle.

With these and other objects in view, the ernbodiments or our invention will be best understood by reference to the following speclcation ing, in the figure there is shown a hollow glass envelope indicated generally at t, the lower part of said glass envelope being formed of glass capable of withstanding a reasonable amount of temperature variation and also one whose characteristics of expansion are similar to certain metals used for electrodes so' that a positive seal may be acquired between the electrodes and the glass. We have found that a glass very satisfactory for 'this purpose is the Nonex glass manufactured by the Corning Glass Works.

The upper half of the glass envelope howeverg,

and that portion indicated at 4, is formed of a glass whose characteristics permit a high percentage of the ultraviolet rays to pass with little dim'culty so that this portion of the tube does not act to lter out the ultraviolet rays, but allows their easy passage. In this instance we have found that^ an ultraviolet transmitting Corex glass, also made by the Corning Glass Works, is satisfactory. These two portions are fused together at the line indicated at t to form a single unitary shell to house the electrodes. This is merely described as illustrating one form which our invention may take. Any envelope which can be made from material which will form a satisfactory seal with the electrodesand pass ultraviolet" light would be satisfactory and our invention should not therefore be limited to the form shown. A

Sealed into the lower portion of the envelope 2 is an electrode 8 staked into one side of a metal band lil, said metal band encircling and being definitely connected to the lower portion of a substantially circular carbon electrode I2.. This assembly is entirely encased in a glass tube i4, which is a sub-assembly, prior to the insertion into the hollow glass envelope which may either be evacuated or filled partially with an inert gas. The upper end of the carbon electrode and the glass tube are ground 01T to form a tapered surface I6. Also sealed into the lower portion of the tube is a second ordinary metallic electrode I8 which projects up into the hollow portion of the tube. A pool of mercury 20` fills the tube up to the approximate center, as indicated,

. thus forming a circuit between the two electrodes.

Connected to the electrode 8 externally-is a line 22 which proceeds to a switch24 connected to the positive side of the battery 26, the negative side of said battery being connected by line 28 towone side of a transformer primary 3U, the Opposite side of said transformer being connected by line 32 to the electrode I8. In the upper portion of the tube and extending directly down and substantially concentric to the assembly of 23 turns and a secondary of 1500 turns operates satisfactorily, -although the ratio is of course not at all critical.

When the switch 24 is closed a circuit is completed from the positive side of the battery through switch 24, line 22, electrode 8, carbon electrode I2, mercury pool 20, electrode I8, line 32, transformer primary 30 and line 28 back to the battery 26. This causes current to flow through the primary 30 and also said current flowing between the carbon electrode I2 Iand the mercury pool 20 causes a heating of the mercury in contact with the carbon surface and in. the manner of mercury interrupters, particularly those of the type disclosed in Ruben Patent No. 2,107,742, will cause the mercury at such contact point to vaporize and thus break the circuit. However, it will immediately recondense and reform thecircuit so that there is an automatic interrupted currentsset up. The electrode I2, as

' before mentioned, has a tapered surface such as shown in I6 and the purpose of this tapering is to provide a better displacement action between the mercury in contact with the carbon surface so that when the mercury is heated to vaporize it will be thrown somewhat to one side in the form of a wave and then flow back against the surface to provide both a `better discharging action of the mercury from the surface and a more even ow back to the surface.

There will of course through this interrupting action at the surface of the mercury and carbon be some arcing and this arcing will be a source of'ultraviolet rays and some will therefore be sent out from this point. The tapered' surface, however, permits the arc at the carbon tip to be exposed. above the mercury on only a slight movement of the mercury away from the surface. This enables operation at higher frequencies and tends to .produce a much steadier light and reduce flicker. However, the amount of these rays is not large, though in some instances it may sufce. By applying the secondary voltage generated through the transformer secondary to the electrode 34, we have found that upon the vapor- .ization of the mercury and the initiation of a small arc at the surface of the carbon the additibnal secondary voltage will cause a large arc `to be set up between the electrode 34 and the l surface of the mercury due to said induced secondary voltage, and this secondary current is substantially in phase with the primary current. The voltage induced inthe secondary is not sufficient itself to cause an arc tc strike between the tioned, is formed of glass which allows the passage of ultraviolet rays. Therefore, as the two lower electrodes I2 and I8 provide the interrupter action for the construction, the third electrode and the attendant voltage induced in the transformerprovides a high voltage flash-over to provide a suiiicient source of ultraviolet ray.

We have found, however, that' there is of course a considerable amount of heat generated during the production of such r'ays and to prevent the burning or pitting of the glass envelope we have inserted therein a small cylindrical member 42 formed of quartz which floats upon the top of the mercury pool 20 and protects the glass envelope portion 4 from Athe direct heatof the arc and therefore prevents the pitting and deterioration and smoking up of the same. If desired, the. quartz cylinder may be anchored to the lead I6. We have also found that the introduction of a very small piece of magnesium foil into the mercury just prior to sealing oif the tube assists substantially in maintaining the mercury in its desired condition and maintains the same very clean and unoxidized, The magnesium alloys very completely with the mercury and therefore vaporzes to a small. degree when the mer-- tomatic, rugged, and will operate from a low voltage source.

We claim: l

1. In a system, a supply of direct current, a transformer having primary and secondary windings connected to the source, interrupter means including an electrode connected in the primary circuit, supporting means for 'the interrupter means and an electrode connected to the secondary and mounted on the said supporting means in spaced relation to the interrupter electrode means but sufliciently close to draw an arc therefrom when the voltage is raised through the transformer action.

2. In a system, a supply of direct current, a transformer having primary and secondary windingsA connected to the supply, autonomic mercury interrupter means connected in the primary transformer circuit and an electrode mounted in juxtaposition to the mercury and connected to the transformer whereby voltage induced by the interruptions in the primary causes the secondary voltage applied to the electrode to be suicient to draw an arc from the mercury.

3. In a system, a supply of direct current, transformer means for increasing voltage having primaryand secondary circuits connected to the supply of current, autonomic mercury interrupter means connected' in the primary circuit, anelectrode connected in the secondary circuit, a common evacuated support for the interrupter means and the electrode, the latter being mounted in spaced relation to the mercury whereby the interrupter action causes some arcing and vaporization of th'e mercury to assist in arcing action between the electrode and the mercury.

4. Ina device of the class described, an insulating envelope, a pair of electrodes sealed in said envelope in spaced relation, one of said electrodes being formed of carbon, a pool of mercury in the envelope extending between said electrodes, a third electrode spaced above the other two and above the mercury pool and adapted when voltage is applied thereto to cause aptnc between the mercury surface and itself and shielding means oating on the surface of the mercury surrounding the arcing area to protect the in side of the envelope against the arc heat. A

5. In a device of the class described, a hollow insulating envelope, a pair of spaced electrodes sealed in the envelope, one of said electrodes being formed of carbon and surrounded by insulating means with the exception of the upper extremity which is cut at an angle to the electrode and thus forms a tapered surface, a pool of mercury extending between the two electrodes but not extending entirely to the top of the carbon electrode, these two electrodes and the mercury forming a current interrupter when current is supplied, the tapered face of th'e carbon providing a cleaner break with the mercury.

6. In a device of the class described, a hollow insulating envelope, a pair of spaced electrodes sealed in the envelope, one of said electrodes being formed of carbon and surrounded by insulating means with the exception of the upper extremity which is cut at an angle to the electrode and thus forms a tapered surface. a pool of mercury extending between the two electrodes but not extending entirely to the top of the carbon electrode, these two electrodes and the -mercury forming a current interrupter when current is supplied, the tapered face of the carbon providing a cleaner break with" the mercury, means for supplying direct current to the electrodes, a third electrode carried by the envelope and spaced above the mercury pool and means for applying a voltage thereto to cause an arc between this electrode and the mercury pool.

7. In a system for generating ultraviolet rays, an insulating envelope, a. plurality of electrodes sealed into said envelope in spaced relation, at least one of said electrodes being formed of carbon, a pool of mercury extending from the carbon electrode to one of the other electrodes, a

transformer having a primary and secondary winding, a source of direct current, said source, transformer primary, and two electrodes being connected in series to provide an automatic interrupter to generate pulsating current and mercury vapor within the envelope, a third electrode being connected to the transformer secondary, said third electrode spaced above the mercury pool whereby the pulsating primary cur- 

